For the customer #CUS_ID with the subscription #SUB_ID the option to change the plan resources ("Buy resources" button in "Store" section) is not available on the "Account" page in CP:
End date" of the affected subscription is in the past already.
There is a Renewal order
Open status that is not paid.
Advise the client to pay the order to renew the subscription.
Or, alternatively, the Provider can process the renewal order with the "
Process Order immediately" button:
PCC > Top > Billing Director > Receivable > Documents > Orders > Order #ORDER_ID > Process Order immediately
This will complete the order and renew the subscription and also create a new invoice for the customer to be paid.
Buy resources" button will appear in CP.